1. Field of the Invention
The present invention relates to a glass fiber strand useful for the preparation of a glass fiber-reinforced thermoplastic resin (FRTP) and a process for producing FRTP.
2. Discussion of Background
Thermoplastic resins are widely used for the production of various products such as parts of electrical and electronical equipments and of automobiles. In a case where a high strength is required, it is common to incorporate reinforcing fibers such as glass fibers into such resins or to form "polymer alloys" by mixing other thermoplastic resins into the thermoplastic resins in which the reinforcing fibers are to be incorporated.
A polymer alloy is a general term for a system prepared by incorporating to a main thermoplastic resin an additional resin (an auxiliary resin) to improve the performance or properties of the main thermoplastic resin. FRTP employing such a polymer alloy as the resin, is prepared by a method of heating and mixing the main thermoplastic resin and the auxiliary resin uniformly to form a polymer alloy and mixing reinforcing fibers thereto, or a method of mixing the above two types of resins and reinforcing fibers simultaneously.
In the former method, the resin is required to be heated twice (when the polymer alloy is prepared and when FRTP is prepared), whereby the process is cumbersome, and the resin is likely to be deteriorated by the heating twice.
The latter method has no such a difficulty, but the resins are required to be weighed and mixed each time, and when the two resins differ in the particle size or in the specific gravity, it tends to be difficult to mix them uniformly, and a fluctuation is likely to result in the quality of the product.
Further, in order to adequately improve the performance of the main thermoplastic resin in either method, a substantial amount of the auxiliary resin is required to be used, but if a large amount of the auxiliary resin is used, other properties of the main thermoplastic resin are likely to deteriorate.
For example, the impact strength of a polycarbonate at a low temperature can be improved by an addition of an impact strength modifier to the polycarbonate. However, in order to remarkably improve the impact strength, the amount of the impact strength modifier is required to be at least 10% by weight, whereby the performance of e.g. the tensile strength tends to deteriorate.